Process for the preparation of n-alkyl beta-alanines



United States Patent PROCESS FOR THE PREPARATION OF N-ALKYL p-ALANINES David Aelony, Minneapolis, Minn., assignor to General Mills, Inc., a corporation of Delaware No Drawing. Application February 23, 1954 Serial No. 412,092

2 Claims. (Cl. 260-482) The present invention relates to the reaction between lower alkyl acrylates and long chain primary amines to form the adduct RNHC H COOR in which R is an aliphatic hydrocarbon chain containing from 8 to 22 carbon atoms and R is a lower alkyl group containing from 1 to 4 carbons atoms. These compounds may be hydrolyzed to form salts which are useful as surface active agents.

Adducts of this type are disclosed in the Isbell Patent 2,468,014. In that patent the reaction mixture was maintained at temperatures of from 25-30 C. It has now been discovered that when operating at temperatures of 25-30 C. the reaction proceeds to form not only the monoadduct referred to above, but also to product substantial quantities of the diadduct RN(C H COOR It has also been discovered that by operating within the temperature range of 50 to 120 C. it is possible to control the reaction to form maximum percentages of the monoadducts. Since the hydrolized products derived from the monoadducts diifer in their properties from the hydrolyzed product of the monoadduct, it is frequently desirable to control the reaction so as to obtain the maximum quantity of each of these products. The present invention involves a process in which the maximum percentages of the monoadducts may be obtained.

In preparing surface active materials by this method, it is imperative that the quantity of unreacted primary amine in the product be maintained at a very low level. Many people experience undesirable skin reactions from contact with long chain primary amines. Accordingly, it is necessary either to insure that substantially all the primary amines are reacted or to employ some process which will remove unreacted amine from the reaction product. The removal of unreacted amine from the reaction product is diflicult and accordingly it is preferred to employ reaction conditions which will insure the complete reaction of the primary fatty amine employed as starting material. In order to insure more complete reaction, it is desirable to employ an excess of the acrylate ester in the addition reaction. However, the use of an excess of the acrylate ester has the tendency to increase the formation of the diadducts. It has been found that by employing an excess of the acrylate ester which is limited to from 10 to 30% of the theoretical quantity and by employing the temperature conditions referred to above it is possible to obtain high yields of the monoadduct with relatively low levels of the diadduct and at the same time substantially completely eliminating the residual primary amine.

It is, therefore, an object of the present invention to provide a novel process of reacting lower alkyl acrylate esters with primary fatty amines in order to obtain the monoadduct referred to above, while at the same time minimizing the formation of the diadduct and also minimizing the residual free primary amine in the reaction product.

The fatty amines which may be employed in the pres- 2 16,911 Patented Dec. 17, 1957 2 en'tinve'ntion are the primary fatty a'minesin which the fatty group contains from 8m 22 carbon atoms. These maybe single isolated fatty amines or may be mixed fatty amines derived from the fatty acids of a fat or oil or from any selected fraction thereof. The amines may be either saturated or unsaturated.

The acrylate esters which may be employed are the lower alkyl acrylates containing from 1 to 4 carbon atoms in the alcohol portion of the ester. These include methyl, ethyl, propyl, and butyl esters. Since methyl acrylate is readily available commercially, it is preferred.

In carrying on the reaction, the amine and the acrylate ester are mixed, the acrylate ester being employed in an excess of from 10 to 30%. A preferred excess of the acrylate is from 15 to 30%. The reaction mixture is heated and agitated at temperatures within the approximate range of 50 to 120 C. The time period will vary depending upon the temperature and the particular ex cess of acrylate employed. At temperatures of 120 C. a time period of 1 hour is suitable whereas at temperatures of 80 to 100 C. up to 4 hours are required. At temperatures of around 60 C. time periods up to 6 hours are necessary. Extended reaction times at 120 C. over and above those required for the formation of the product are undesirable inasmuch as there is some tendency for the formation of the amino amide The following examples will serve to illustrate the invention:

Dodecyl amine (187 g.) was heated to 60 C. Methyl acrylate (103 g., 20% excess) was added at once and Per- Percent Percent Percent See. No. Temp., Time, cent Amine primary sec. tert. amine] O. hours excess No. amine amine amine rt.

amine 1... -90 4 20 200. 1 2. 2 83. 8 l2. 6 6. 65 2- 80-90 4 30 197. l O 83. 9 14. 2 5. 9 3 120 4 10 192. 2 4. 9 77. 5 10. 9 7. l8 4.-.. 60 6 10 202. 0 7. 1 79. 8 9. 8 8. 1 5. 6 10 194.0 4.8 82.6 8.2 10.0 6.-.- 1 30 202. 7 3. 5 85. 5 9. 6 8.9

I hereby claim as my inventlonz 1. Process of preparing compounds having the formula RNHC H COOR in which R is an aliphatic hydrocarbon group containing from 8 to 22 carbon atoms and R is a lower alkyl group containing from 1 to 4 carbon atoms which comprises reacting the corresponding amine RNH with the corresponding lower alkyl acrylate ester, the ester being employed in an excess of from 10-30%, at temperatures within the approximate range of 50- 120 C.

2. Process of preparing compounds having the formula RNHC H COOR in which R is an aliphatic hydrocar- 3 w 4 bon group containing from 8-22 carbon atoms and R References Cited in the file of this patent is a lower alkyl group containing from 1 to 4 carbon UNITED STATES PATENTS atoms which comprises reacting the corresponding amino RNH with the corresponding lower alkyl acrylate ester, 2,017,537 Hoffman et 1935 the ester being employed in an excess of from 15-30%, at 5 2,438,091 Lynch 1948 2,468,012 Isbell Apr. 19, 1949 t t 'thi th t {so-120 c.

empem n e appmxma flange 2,720,536 Aelony et a1. Oct. 11, 1955 

1. PROCESS OF PREPARING COMPOUNDS HAVING THE FORMULA RNHC2H4COOR1 IN WHICH R IS AN ALIPHATIC HYDROCARBON GROUP CONTAINING FROM 8 TO 22 CARBON ATOMS AND R1 IS A LOWER ALKYL GROUP CONTAINING FROM 1 TO 4 CARBON ATOMS WHICH COMPRISES REACTING THE CORRESPONDING AMINE RNH2 WITH THE CORRESPONDING LOWER ALKYL ACRYLATE ESTER, THE ESTER BEING EMPLOYED IN AN EXCESS OF FROM 10-30%, AT TEMPERATURES WITHIN THE APPROXIMATE RANGE OF 50120*C. 